1. Field of the Invention
This invention relates to a novel ceramic composite material having high magnetic saturation magnetization. More specifically, it is directed to a ferromagnetic metal/ceramic composite having high electrical resistivity and high saturation magnetization for use in self-inductance coils, transformers, tuners and filters and magnetic recording media.
2. Description of the Prior Art
Ferrites of the general formula MA.sub.2 O.sub.4, M being a divalent metal such as Mg, Mn, Fe, Co, Ni or Cu, and A being a ferromagnetic metal, such as Fe, Co or Mn, are used in self-inductance coils, transformers, tuners, filters and magnetic recording media. In such materials, a high electrical resistivity is required since it provides for low induced eddy currents and low heat dissipation when a high-frequency alternating magnetic field is imposed. A high saturation magnetization, on the other hand, is desirable since it provides high magnetic flux densities, high magnetic coupling between transformer primary and secondary windings and high self-inductance with a small amount of magnetic core material, making it possible to achieve desired electric circuit characteristics with small components. Furthermore, a high Curie temperature is desirable since it allows operation of such components at elevated temperature without loss of desirable high magnetic permeability.
Iron particles dispersed in a silica matrix, and iron and cobalt particles dispersed in a boron nitride matrix, have been produced by a process referred to as sputtering (J.Appl.Phys. 64(8) 1988 and J.Appl.Phys. 61(8) 1987).
U.S. Pat. No. 3,234,487 discloses a waveguide section for dissipating microwave energy made of iron powder dispersed in glass, made by mixing iron powder and powdered glass and sintering.
U.S. Pat. No. 3,748,270 discloses cobalt-doped magnetic iron oxide prepared by mixing alpha-hematite or alpha-ferric hydroxide with a cobalt oxide or a cobalt salt, heat treating the mixture, and cooling in an inert atmosphere.
U.S. Pat. No. 3,974,246 discloses cobalt-substituted magnetite subjected to a magnetic field and annealed to improve the magnetic properties of the material.
U.S. Pat. No. 4,538,151 discloses a material for absorption of microwave energy having short fibers of metal or metal alloy and ferrite particles embedded in a matrix of an organic polymer such as polyethylene or polybutadiene.
U.S. Pat. No. 4,543,197 discloses magnetic ferrites of Fe, Mn, Ni, Cu, Mg, Zn or Co prepared by mixing a ferroalloy and metal oxide powder in water, ventilating with air to oxidize the ferroalloy to metal oxides, drying and heat treating.
U.S Pat. No. 4,626,370 discloses a magnetic fluid comprising fine iron particles dispersed in a phospholipid such a lecithin, alkyl esters of dicarboxylic acids, and an antioxidant such as d,l-alpha-tocopherol (vitamin E).
U.S. Pat. No. 4,865,709 discloses a magnetron sputter apparatus for forming a film of powder under vacuum by exposing a target material having a geometry designed to optimize film formation and uniformity of film thickness to sputtering.